1. Technical Field
The present invention relates to a wireless data network and more specifically to managing energy consumption related to data processing and communication in sensor networks.
2. Background Art
Networking of unattended sensors is expected to have a significant impact on the efficiency of many military and civil applications, such as security and disaster management. These systems process data gathered from multiple sensors to monitor events in an area of interest. Sensors in such systems are typically disposable and expected to last until their energy drains. Therefore, energy is a very scarce resource for such sensor systems and has to be managed wisely in order to extend the life of the sensors for the duration of a particular mission.
Sensors are generally equipped with data processing and communication capabilities. A sensing circuit measures parameters from the environment surrounding the sensor and transforms them into an electric signal. Processing such a signal reveals some properties about objects located and/or events happening in the vicinity of the sensor. The sensor communicates such sensed data, usually via a radio transmitter, to a command center either directly or through a data concentration center (a gateway). The gateway can perform fusion of the sensed data in order to filter out erroneous data and anomalies and to draw conclusions from the reported data over a period of time. For example, in a reconnaissance-oriented sensor network, sensor data indicates detection of a target while fusion of multiple sensor reports are used for tracking and identifying the detected target.
Signal processing and communication activities are the main consumers of sensor's energy. Since sensors are battery-operated, keeping the sensor active all the time will limit the duration that the battery can last. Therefore, optimal organization and management of the sensor network are very crucial in order to perform the desired function with an acceptable level of quality and to maintain sufficient sensor energy to last for the duration of the required mission. Mission-oriented organization of the sensor network enables the appropriate selection of only a subset of the sensors to be turned on and thus avoids wasting the energy of sensors that do not have to be involved.
In wired networks, the emphasis has traditionally been on maximizing end-to-end throughput and minimizing delay. In general, paths are computed to minimize hop count or delay. While wireless networks inherited such design metrics from their wired counterparts, energy constraints and signal interference have become central issues. Signal interference has received the most attention from the research community due to the growing popularity of wireless consumer devices.
There is a need to increase energy efficiency, especially when a network consists of remotely deployed unattended sensors. Previous art has focused on improving hardware-related energy efficiency aspects of wireless communications. Low-power electronics, power-down modes, and energy efficient modulation are examples of work in this category.
Energy-aware routing has started to receive some attention in the recent few years, motivated by advances in wireless mobile devices. Since the overhead of maintaining the routing table for wireless mobile networks is very high, the stability of a route becomes a major concern. It is known that battery power capacity, transmission power, and stability of routes are among the issues to be considered in designing a power efficient routing protocol. Algorithms have been proposed to select the routes such that the nodes' batteries drain-out time is maximized. The reported results have indicated that in order to maximize the lifetime, the traffic should be routed such that the energy consumption is balanced among the nodes in proportion to their energy reserves.
There remains a long-felt need for methods of energy-aware network management that will ensure a desired level of quality-of-service (QoS) for data transfer as well as maintaining the life of the network.